This invention relates to a displacement sensor for detecting very minute displacements and vibrations directly in the form of electric signals.
For electrical detection of displacements and vibrations, it has been customary to adopt sensors of the type which utilize variation in capacitance, induction, etc. These sensors have the disadvantages that they necessitate complex configurations which take up a large amount of space, that they do not always respond linearly to displacements or that they issue electrical outputs in differential forms in response to vibrations, and that their outputs, therefore, are not in the form of numerical values directly proportional to vibrations or displacements. The sensor which utilizes the function of a differential transformer and serves to detect very minute displacements has the disadvantages that it has a large mass and fails to detect minute vibrations. The sensor of the type which utilizes the phenomenon of electromagnetic induction has an electrical output which is proportional to the velocity of movement and not to the amount of displacement as is observed in the pickup head of a phonograph and, therefore, has the disadvantage that it issues a very small output in response to vibrations of a low frequency.
If a sensor is to provide extremely accurate measurement, all the components of this sensor are naturally required to be fabricated with high precision, which is very difficult to obtain.
The main object of this invention is to provide a displacement sensor capable of detecting displacements or vibrations on the sub-micron order in a non-contact state.
Another object of this invention is to provide a displacement vibration sensor of very small size and simple configuration, which enjoys improved properties and novel functions unattainable by the conventional countertypes, namely a displacement sensor that produces an electrical output proportional to the amount of displacement or, in response to a large displacement, generates an output directly in the digital pulse signals and that, when used for the detection of vibrations, issues an electrical oscillatory output proportional to the displacement involved without reference to the frequency.